The paper gives the EM absorbed dose for man and animals at various frequencies for the plane wave irradiation condition for different orientations of the body relative to incident fields. Also included are the results for the whole-body absorption for conditions of electrical contact with ground and in the presence of reflecting surfaces of high conductivity and multiple animals. The data are given for the ditribution of power deposition in man models for the resonance conditions of highest whole-body electromagnetic absorption. The highlights of the results obtained with proportionately scaled saline- and biological-phantom-filled models of man have been confirmed by experiments with small laboratory animals, from 25-g mice to 2250-g rabbits.

State of the knowledge for electromagnetic absorbed dose in man and animals

Generalized curves are given for rates of whole-body absorption of electromagnetic energy by models of human beings as a function of frequency. Exposures were made in free space, or when the model made electrical contact with the ground. The effects of the presence of reflecting surfaces also were analyzed. Peaks of absorption with and without a ground, are projected, respectively, to be (31 to 34 MHz) and (62 to 68 MHz) × (1.75/height of model in meters). Rates of energy deposition are given for models of man and for animals subjected to radiation at a power density of 10 mW/cm2 for the various conditions of exposure. At resonance, values of whole-body absorption as high as 4,077 to 8,154 watts for the adult human being are predicted. The times-to-convulsion of ∼100-g rats at power densities of 3 to 20 mW/cm2 confirmed predictions of extremely high rates of absorption in the presence of reflecting surfaces.

Deposition of electromagnetic energy in animals and in models of man with and without grounding and reflector effects

Image theory has been used to obtain moment-method solutions of the deposition of electromagnetic energy in standard man as a function of grounding and reflector effects. The calculated values are in good agreement with experimental data. For the EIĽ orientation, the resonant frequency of standard man shifts from 77 MHz in free space to 47 MHz when standing on a ground plane. The dependence of reflector effects on spacing and frequency are in agreement with the gain enhancement calculated for dipoles by antenna theory.

Numerical calculation of electromagnetic energy deposition in models of man with grounding and reflector effects

Radiation patterns were measured for corner-reflector antennas having various combinations of widths and lengths of the reflecting surfaces. The widths of these ranged from 1 to 10 wavelengths, the lengths from 0.5 to 5 wavelengths. The aperture angle was, in general, set at a value required to maximize the gain. Radiation patterns are arranged according to the size of the reflecting surfaces. The effect of the widths and lengths of the surfaces on the widths of the main lobe and on the level of the radiation to the rear is summarized in a series of curves. A corner-reflector antenna with a collinear array of dipoles was designed, constructed, and tested to have sidelobe radiation below -40-db level.

Radiation patterns of finite-size corner-reflector antennas

Radiation pattern and gain of a corner reflector antenna finite in width are calculated by means of geometrical method for diffraction. The functions F(T)s referred to diffraction by the edges and their images are introduced. In the case of an aperture angle not equal to 2\pi /m ( m : integer) a finite number of images of a dipole are considered, and the waves diffracted by the apex edge are introduced. The cases of aperture angles 90\deg , 45\deg and 115\deg are computed. The results are compared with the measured results obtained by Cottony and Wilson. In the forward and lateral directions agreements between both results are very good; however, in the rear direction it may be necessary to take into account the effects of the waves diffracted by the upper and lower edges of the reflector, when the length of the corner reflector is not too great.

On the radiation pattern of a corner reflector finite in width

An experimental comer reflector was erected at the Table Mesa antenna range near Boulder. The aperture angle of this antenna was made adjustable to any value between 20 and 180 degrees. The widths and lengths of the reflecting surfaces were each adjustable from 0.4 to 5.0 wavelengths. Measurements of gain were made for numerous combinations of lengths and widths of reflecting surfaces. These measurements were made with a half-wave dipole in the first, second and third maximum positions. The aperture angle was adjusted to maximize the gain. The principal results are presented in the form of contours of constant gain plotted for a range of widths and lengths of reflecting surfaces from 0.4 to 5.0 wavelengths. These graphs should be useful to a designer of corner-reflector antennas.

A. Wilson

Papers

Gains of finite-size corner-reflector antennas